In general, industrial methods that implement a fluidized bed reactor require means to be installed enabling the particulate materials constituting the fluidized bed(s) inside the reactor to be emptied either totally or in part in order to facilitate operating the reactor.
Partial emptying must be possible while the reactor is in operation since it constitutes one of the ways of controlling changes in the level of the bed, particularly when the level is rising. This occurs, for example, when the flow of elutriated inert particles is less than the mass flow rate of inert particles entering a combustion reactor.
Total emptying is required in order to proceed with periodic inspections of the reactor or during emergency stops of an installation.
These emptying devices must satisfy several severe requirements that result essentially from the physical and thermal characteristics of the bed in operation. These devices are subjected to mechanical and thermal stresses which are large since they are in contact with a medium which is often highly abrasive, at high temperature, and which exerts significant pressure. Since, in addition, they provide communication between the bed and the outside, they often need to provide sealed closure of the enclosure and must be thoroughly cooled in operation in order to ensure safety of equipment and personnel. They must also occupy minimum bulk in order to be capable of being controlled automatically without disturbing the fluidization hydrodynamic regime.
Devices known in the past for performing this function satisfy these requirements to a limited extent only. Overflow orifices are known, as are purge drains disposed vertically or at a very steep slope in the bottom of the fluidization enclosure and fitted with cellular air locks or with guillotine traps for closure or opening purposes.
Devices are also known having transfer fluidized beds or cooled Archimedes screws for extracting particles associated with classifiers.
Most of these systems are disposed at the ends of vertical or very steeply sloping ducts and which are filled with material when the device is not operating, said material forming a plug or blocking the mechanisms due to the fact that said material clogs, compacts, and may even agglomerate by chemical or thermal reaction with these ducts often suffering from hot spots.
In addition, the height of these ducts is a factor that increases the hydrostatic pressure exerted on the extraction devices, thereby making sealing more difficult to achieve.
Finally, in addition to the drawbacks relating to the large size of these devices and to the complexity of the cooling means they require, it is often necessary to provide special equipment downstream for processing and taking up the products extracted in this way from the fluidized bed.
The invention seeks to remedy these drawbacks by providing a device of much simpler design for extracting particulate material, the device being easy of access and protected from the thermal point of view (when applied to a heat generator), and being very easily connected to an automatic mechanism for controlling its operation.